"Shark populations are at dangerously low levels in parts of the Great Barrier Reef, with estimations placing reef shark populations at 3 to 12 per cent of their original size in some 'regular use' areas.

"This is simply not good enough. We must do more to protect these top predators from disappearing on our watch, if not for the benefit of the environment, then at least for the benefit of the back pocket."

A recent James Cook University study funded by the Marine and Tropical Sciences Research Facility found potential shark sightings to be a major drawcard to the diving sector, with tourists willing to pay thousands of dollars to see a shark in its natural environment.

The study found the average live-aboard dive passenger spent at least $5,000 while in the Cairns / Port Douglas area of Far North Queensland, with many attracted to the region by the opportunity to view sharks in the wild.

The researchers estimated up to 25 per cent (or $1,375) of each visitor's expenditure was directly attributable to the opportunity to see sharks.

Internationally, similar results have been recorded. A study in the Maldives - a popular tourist and diving destination in the Indian Ocean - estimated the value of one grey reef shark to be worth US$3,300 per year to the Maldivian tourism industry as opposed to the one-off value of US$32 to a fisherman.

"It is believed up to 500,000 divers photograph and swim with sharks every year. Not only are shark sightings considered to be one of the most significant of all wildlife interactions but the predator's presence at the top of the food chain is critical to ensuring a healthy and sustainable marine environment."

The JCU research found divers most wanted to see a hammerhead shark in the wild, followed by the whale shark and tiger shark.

Sharks are under particular threat due to their conservative life history traits which are characterised by slow growth rates, late sexual maturity, long gestation periods and birthing only a few young at a time.

They are also particularly threatened by overfishing, accidental bycatch and habitat loss.